Semiconductor Device

ABSTRACT

To realize a semiconductor device including a capacitor element capable of obtaining a sufficient capacitor without reducing an opening ratio, in which a pixel electrode is flattened in order to control a defect in orientation of liquid crystal. A semiconductor device of the present invention includes a light-shielding film formed on the thin film transistor, a capacitor insulating film formed on the light-shielding film, a conductive layer formed on the capacitor insulating film, and a pixel electrode that is formed so as to be electrically connected to the conductive layer, in which a storage capacitor element comprises the light-shielding film, the capacitor insulating film, and the conductive layer, whereby an area of a region serving as the capacitor element can be increased.

BACKGROUND OF THE INVENTION

This application is a continuation of copending U.S. application Ser.No. 11/007,052, filed on Dec. 8, 2004 which is a continuation of U.S.application Ser. No. 10/254,280, filed on Sep. 25, 2002 (now U.S. Pat.No. 6,831,297 issued Dec. 14, 2004).

1. Field of the Invention

The present invention relates to a liquid crystal display device inwhich a semiconductor device such as a transistor formed on aninsulator, in particular, a field effect transistor, and typically a MOS(metal oxide semiconductor) transistor, a thin film transistor(hereinafter, referred to as TFT) is used as a switching element in apixel portion. The present invention also relates to a liquid crystaldisplay device including a circuit or a driving circuit manufactured byusing the semiconductor device, and to an electric appliance in whichthe liquid crystal display device is used for a display portion.

2. Description of the Related Art

Recently, there has been growing a use of the liquid crystal displaydevice in a monitor of a personal computer or a display device of atelevision, in which liquid crystal is interposed between a pair ofsubstrates and an electric field is applied to the pair of substrates toperform a display through a liquid crystal orientation.

Further, due to an improvement in a technique of crystallizing asemiconductor film, the liquid crystal display device is also realizedin which a driving circuit is incorporated into one substrate.

Here, for the TFT of the driving circuit, high field effect mobility isrequired, whereas low leak current characteristics are required for theTFT used as the switching element in each pixel of the pixel portion.Thus, it is important to hold a charge (signal) and even a slight amountof leak current generated during a holding time at which the TFT is inan OFF state causes a deterioration of an image quality and a decreasein a contrast.

However, the TFT involves such a problem that when a semiconductor layeris irradiated with a light, optical excitation occurs to generate anoptical leakage current. Therefore, it is important that alight-shielding film for covering the TFT is formed to block the lightsufficiently to thereby prevent the light irradiation to thesemiconductor layer or, assuming that a leak current is generated, it isimportant to secure a storage capacitor large enough to hold a signal inone frame period even in such a case.

Thus, as a structure in which a storage capacitor is formed and furthera leak light can be shielded, a cell is disclosed in JP 2924506 B, inwhich a source electrode and a drain electrode are formed before aninterlayer film is formed and a light-shielding film made of aluminum isformed on the interlayer film and subjected to anodic oxidation to forman anodized film made of Al₂O₃ on a top surface and a side surface ofthe light-shielding film, and then a transparent pixel electrode isformed thereon to complete the cell including the storage capacitorconsisting of the light-shielding film, an Al₂O₃ film, and thetransparent pixel electrode that are arranged in the stated order.

An electrostatic capacitance (hereinafter, referred to as a capacitance)of a storage capacitor element is in inverse proportion to a thicknessof a capacitor insulating film (in this specification, referred to as adielectric film sandwiched between a pair of electrodes constituted of aconductor) and in proportion to a dielectric constant of the capacitorinsulating film and a surface area of the electrode. Therefore, in thestructure disclosed in JP 2924506 B, since the capacitor insulating filmbetween the light-shielding film and the transparent pixel electrode ismade of the anodized film and maintained almost constant, a region wherethe light-shielding film and the transparent pixel electrode overlapeach other can substantially function as the storage capacitor element.

However, in the liquid crystal display device, there arises a problem inthat a defective display is caused by a defect in orientation of theliquid crystal. The defect in orientation of the liquid crystal occursas follows. Steps or unevennesses on the surface of the pixel electrodeaffect the surface of an orientation film and involve uneven rubbing onthe orientation film, and finally causes the defect in orientation ofthe liquid crystal and the deterioration of the image quality. In thestructure disclosed in JP 2924506 B, as shown in FIG. 1A, the step ofthe pixel electrode exists in a portion outside a light-shielded regionby the light-shielding film (a region transmissive of light) and therearises a problem in that the light accidentally passes therethrough dueto the defect in orientation of the liquid crystal, or the like.

However, in the display device including a laminate structure consistingof a number of layers, it is unavoidable that the steps or unevennessesoccur on the surface of the pixel electrode and affect the surface ofthe orientation film as well, followed by decrease in the contrast dueto a light accidentally passing therethrough. Thus, a method offlattening the steps or unevennesses of the pixel electrode,particularly, a region transmissive of light which contributes to adisplay of the pixel has been considered.

Thus, a method is devised in which the light-shielding film is formed onan element substrate side and the step caused through the formation isflattened to form the pixel electrode. However, according to thismethod, when the storage capacitor element is formed between thelight-shielding film and the pixel electrode, as shown in FIG. 1B, aninterlayer distance is made large between the light-shielding film andthe pixel electrode to thereby make a region functioning as thecapacitor element narrow, with the result that it is impossible tosecure the sufficient storage capacitor.

Due to a slight amount of off-leak current flowing while the TFT is inan OFF state, the decrease in the contrast and a nonuniform imagequality as a panel are caused, so that it is unavoidable that thestorage capacitor element is formed for complementation thereof.However, if the storage capacitor element is formed in another region,for example, as shown in FIG. 1C, if the storage capacitor element isconstituted of a semiconductor layer, a gate insulating film, and aconductive layer formed on the gate insulating film with an active layerof the TFT extended, an opening ratio of the pixel becomes small, sothat a display capacity is decreased in terms of brightness.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentionedproblem, and an object of the present invention is to realize asemiconductor device including a capacitor element capable of obtaininga sufficient storage capacitor without reducing an opening ratio, inwhich a pixel electrode is flattened in order to control a defect inorientation of liquid crystal.

According to the present invention, there is provided a semiconductordevice, including: a thin film transistor; a storage capacitor element;a light-shielding film formed on the thin film transistor; a capacitorinsulating film formed on the light-shielding film; a conductive layerformed on the capacitor insulating film; an insulating film formed onthe conductive layer; and a pixel electrode formed on the insulatingfilm, in which: the conductive layer and the pixel electrode areelectrically connected; and the storage capacitor element is composed ofthe light-shielding film, the capacitor insulating film, and theconductive layer.

Also, according to the present invention, the semiconductor deviceincludes: a light-shielding film formed on a thin film transistor; acapacitor insulating film formed on the light-shielding film; aconductive layer formed on the capacitor insulating film; an insulatingfilm formed on the conductive layer; and a pixel electrode formed on theinsulating film, in which: the storage capacitor element is composed ofthe light-shielding film, the capacitor insulating film, and theconductive layer; and the conductive layer and the pixel electrode arebrought into contact with each other through an opening formed in theinsulating film, the opening formed on the light-shielding film.

Further, according to the present invention, there is provided thesemiconductor device, including: a thin film transistor; a storagecapacitor element; a light-shielding film formed on the thin filmtransistor; a capacitor insulating film formed on the light-shieldingfilm; a conductive layer formed on the capacitor insulating film; aninsulating film formed on the conductive layer; and a pixel electrodeformed on the insulating film, in which: the storage capacitor elementis composed of the light-shielding film, the capacitor insulating film,and the conductive layer; the conductive layer and the pixel electrodeare brought into contact with each other through an opening formed inthe insulating film; the insulating film is formed so that a step of thepixel electrode caused by the capacitor insulating film and theconductive layer is flattened; and an inner wall of the opening and thestep are formed on the light-shielding film.

Further, according to the present invention, there is provided thesemiconductor device, including: a thin film transistor; a storagecapacitor element; a light-shielding film formed on the thin filmtransistor; a capacitor insulating film formed on the light-shieldingfilm; a conductive layer formed on the capacitor insulating film; aninsulating film formed on the conductive layer; and a pixel electrodeformed on the insulating film, in which: the storage capacitor elementis composed of the light-shielding film, the capacitor insulating film,and the conductive layer; the conductive layer and the pixel electrodeare brought into contact with each other through an opening formed inthe insulating film; and the insulating film is formed so that a stepbetween one pixel electrode and other pixel electrode adjacent theretois flattened.

Further, according to the present invention, there is provided thesemiconductor device, including: a thin film transistor; a storagecapacitor element; a light-shielding film formed on the thin filmtransistor; a capacitor insulating film formed on the light-shieldingfilm; a conductive layer formed on the capacitor insulating film; aninsulating film formed on the conductive layer; and a pixel electrodeformed on the insulating film, in which: the storage capacitor elementis composed of the light-shielding film, the capacitor insulating film,and the conductive layer; the conductive layer and the pixel electrodeare brought into contact with each other through an opening formed inthe insulating film; and the conductive layer and the pixel electrodeare aligned at end surfaces thereof between adjacent pixels.

Further, according to the present invention, there is provided thesemiconductor device, including: a thin film transistor; a storagecapacitor element; a light-shielding film formed on the thin filmtransistor; a capacitor insulating film formed on the light-shieldingfilm; a conductive layer formed on the capacitor insulating film; aninsulating film formed on the conductive layer; and a pixel electrodeformed on the insulating film, in which: the storage capacitor elementis composed of the light-shielding film, the capacitor insulating film,and the conductive layer; the conductive layer and the pixel electrodecontact through an opening formed in the insulating film; and thecapacitor insulating film, the conductive layer, and the pixel electrodeare separately formed in each of pixels and are aligned at end surfacesthereof between the adjacent pixels.

The conductive layer formed on the capacitor insulating film iselectrically connected to the pixel electrode so as to make a potentialequal therebetween and the storage capacitor element composed of thelight-shielding film, the capacitor insulating film formed on thelight-shielding film, and the conductive layer formed on the capacitorinsulating film is adapted thereto, so that a sufficient storagecapacitor can be obtained without reducing an opening ratio.

Also, on the conductive layer, a flattening film formed of theinsulating film is formed in order to prevent the defect in orientationof the liquid crystal due to the steps or unevennesses on the surface ofthe pixel electrode in a region through which a light is passed (regioncontributing to a display). Through the formation of the flatteningfilm, since the step of the pixel electrode is formed on thelight-shielding film, even if an uneven rubbing treatment is performedon the orientation film to cause the defect in orientation, it does notaffect a display.

Note that, according to the present invention, the liquid crystal issandwiched between a pair of substrates and the thin film transistor isused as a switching element for each pixel. The present invention can beadapted to all liquid crystal display devices including a liquid crystaldisplay device connected to a driving circuit through a connector suchas an FPC or a TAB, a liquid crystal display device in which a pixelportion and a driving circuit are integrally formed on the samesubstrate (hereinafter, referred to as integrally formed liquid crystaldisplay device), a liquid crystal display device in which the drivingcircuit is faulted in the integrally formed liquid crystal displaydevice and the pixel portion is connected with a controller having afunction of displaying an image, and a liquid crystal display deviceprovided with a microcomputer for controlling the controller. Further,in this specification, all the liquid crystal display devices describedabove collectively refer to the semiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1C are views for illustrating a conventional storagecapacitor element;

FIGS. 2A and 2B are views for illustrating a region functioning as astorage capacitor element according to the present invention;

FIGS. 3A and 3B are views for illustrating a region functioning as theconventional storage capacitor element;

FIGS. 4A to 4C are views for showing an embodiment of the presentinvention;

FIGS. 5A and 5B are views for showing an embodiment of the presentinvention;

FIG. 6 is a view for showing an embodiment of the present invention;

FIG. 7 is a view for showing an embodiment of the present invention;

FIGS. 8A and 8B are views for showing an embodiment of the presentinvention;

FIGS. 9A to 9D are views for showing an embodiment of the presentinvention;

FIGS. 10A and 10B are views for showing an embodiment of the presentinvention;

FIGS. 11A to 11D are views for showing an example of an electricappliance;

FIGS. 12A to 12F are views for showing an example of electricappliances; and

FIGS. 13A to 13C are views for showing an example of electricappliances.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this embodiment mode, a description will be given of a structure of apixel portion in a semiconductor device of the present invention.

The structure of the semiconductor device of the present invention isshown in FIG. 2A. A TFT 11 is formed on a substrate 10. The TFT includesa semiconductor layer 12 having at least a channel formation region anda source/drain region, a gate insulating film 13 formed on thesemiconductor layer 12, and a gate electrode 14 formed on the gateinsulating film 13, and further, a source wiring 15 a and a drain wiring15 b which are used for connecting the respective TFTs are formed.

The source wiring 15 a and the drain wiring 15 b are respectivelyconnected to regions (the source region and the drain region) added withan impurity element at a high concentration.

Also, an interlayer insulating film 16 is formed on the gate electrode14, the source wiring 15 a, and the drain wiring 15 b, and alight-shielding film 17 for shielding the TFT (particularly, the channelformation region) from the light is formed on the interlayer insulatingfilm 16.

On the light-shielding film 17, a capacitor insulating film 18 isformed. A conductive layer 19 is formed on the capacitor insulating film18. After the conductive layer 19 is formed, a flattening film 20 madeof an insulating material is formed, followed by a formation of a pixelelectrode 21. The conductive layer 19 and the pixel electrode 21 are incontact with each other through a contact hole formed in the flatteningfilm 20 and are formed so as to make their potentials equal. In thisway, a structure is obtained in which a step (an end portion of thelight-shielding film 17) 22 caused by covering the light-insulating film17 with the insulating film is positioned not in a region through whicha light passes but on the light-shielding film 17. A pixel structuredisclosed in the present invention is characterized in that the storagecapacitor is composed of the capacitor insulating film 18 formed on thelight-shielding film 17 and the conductive layer 19 formed on thecapacitor insulating film 18.

Further, it is characterized in that disturbance in orientation of theliquid crystal due to a step in a region through which a light passes issuppressed.

Note that, the light-shielding film 17 may have a single-layer structureor a laminate structure using an element selected from the groupconsisting of Al, Ti, W, and Cr or an alloy material mainly containingthe above element.

Also, the capacitor insulating film 18 may be composed of an inorganicinsulating film such as a silicon oxide film, a silicon nitride film, asilicon nitride oxide film, or a silicon oxynitride film, which isformed by a CVD method, a sputtering method, etc. Here, it is alsopossible to employ an organic insulating film as long as it hascharacteristics of high dielectric constant and low leak current.

Further, the conductive layer 19 is formed by using an element selectedfrom the group consisting of Al, Ti, and W or an alloy material mainlycontaining the above element, or ITO. Note that, when a priority isgiven to the light-shielding property for the TFT, the conductive layer19 may be formed by using an element selected from the group consistingof Al, Ti, and W or an alloy material mainly containing the aboveelement, which is high in the light-shielding property.

Also, the interlayer insulating film 16 formed on the drain wiring 15 band the light-shielding film 17 formed on the interlayer insulating film16 can be used to constitute the storage capacitor.

In addition, the flattening film 20 composed of the insulating film maybe formed by using a silicon oxide film, a silicon oxynitride film, asilicon nitride oxide film, a silicon nitride film, or other inorganicinsulating films, for example, made of a solution application systemmaterial called SOG (spin on glass). Alternatively, it may be composedof an organic insulating film formed by using at least one kind ofmaterial selected from the group consisting of acrylic resin andpolyimide.

According to the present invention, the conductive layer 19 is formed tomake the pixel electrode and the conductive layer have the samepotential, so that the whole region where pixel electrode overlaps theupper light-shielding film can serve as the storage capacitor element.Therefore, as compared with the conventional structure shown in FIG. 1B,the storage capacitor can be made larger.

As an example of the present invention, an actual view of a mask isshown in FIG. 2B (here, in one pixel designed in a size of 14 μm×14 μm,the light-shielding film and the pixel electrode (ITO) are shown forsimplicity). Here, assuming that calculation is performed on an area ofthe region serving as the storage capacitor element composed of theupper light-shielding film, the capacitor insulating film, and theconductive layer (at the same potential as the pixel electrode), thearea becomes 63.645 μm². In the conventional structure having noconductive layer as shown in FIG. 1B, an area of the region actuallyserving as the storage capacitor element is considerably small incomparison with the present invention, even if the upper light-shieldingfilm and the pixel electrode are overlapped. In FIG. 3B, a regionserving as the storage capacitor element is indicated by the brokenline. In this case, similarly to FIG. 2B, in one pixel designed in asize of 14 μm×14 μm, the light-shielding film and the pixel electrode(ITO) are shown for simplicity. An area of the region serving as thestorage capacitor element is 34.905 μm² in the conventional structure.As compared with the present invention, the present invention canincrease the area serving as the storage capacitor element up to 1.82times the conventional one without reducing the opening ratio.

As described above, the step formed in a region through which a lightpasses in the pixel electrode can be eliminated without additionalsteps. As a result, the steps or unevennesses of the pixel electrode donot hinder the sufficient rubbing treatment for the orientation film, sothat it is possible to suppress the phenomenon of leak light due to thedisturbance in orientation of liquid crystal. Further, as compared withthe conventional structure having no conductive layer, by forming theconductive layer 19, the capacitor approximately twice the conventionalone can be secured without reducing the opening ratio, so that thepresent invention is effective.

Note that, the present invention can be adapted without being limited tothe TFT described in this embodiment mode.

Embodiment 1

A method of manufacturing an active matrix substrate is explained inEmbodiment 1 using FIGS. 4A to 6. A substrate on which driver circuits,and a switching element in the pixel portion (the pixel TFTs) andstorage capacitor elements are formed is referred to as an active matrixsubstrate in Embodiment 1, for convenience.

First, a substrate made from glass, such as barium borosilicate glass oraluminum borosilicate glass, typically Corning Corp. #7059 glass, #1737glass, and the like is used as a substrate in Embodiment 1. Note thatquartz substrates, silicon substrates, and metallic substrates andstainless steel substrates on which an insulating film is formed mayalso be used as the substrate. Further, plastic substrates having heatresistant properties capable of withstanding the processing temperaturesof Embodiment 1 may also be used. A quartz glass substrate is applied inEmbodiment 1.

A lower portion light shielding film 101 is formed next on the quartzsubstrate 100. The lower portion light shielding film 101 has a singlestructure or a laminate structure that is formed out of conductivematerials composed of one element selected from Ta, W, Cr, and Mo havingheat resistant properties capable of withstanding the processingtemperatures of this embodiment, or conductive materials composed ofsaid elements-based alloy, at a film thickness on the order of 300 nm.The lower portion light shielding film 101 functions as a gate wiring,so that it is also referred to as a gate wiring. A 75 nm thickcrystalline silicon film is formed in Embodiment 1, and after forming a150 nm thick WSix film (where x=2.0 to 2.8), unnecessary portions areetched, the lower portion light shielding film 101 is formed. Note thatalthough a single layer structure is used as the lower portion lightshielding film (the gate wiring) 101 in Embodiment 1, a laminatestructure having two or more layers may also be used. The interlayerinsulating film may be formed before the lower portion light shieldingfilm 101 is formed in order to prevent the dispersion of pollutionmaterials.

A base insulating film 102 is then formed on the substrate 100 and thelower portion light shielding layer (gate wiring) 101 having a filmthickness of 10 to 650 nm (preferably between 50 and 600 nm) from aninsulating film such as a silicon oxide film formed by LPCVD at hightemperature of 800° C., a silicon nitride film, or a silicon oxynitridefilm. A single layer structure is used as the base insulating film 102in Embodiment 1, but a laminate structure in which two or more layers ofthe insulating films are laminated may also be used to prevent thediffusion of pollution materials. A silicon oxynitride film made formedby plasma CVD using SiH₄, NH₃, and N₂O as reactant gas is formed as thebase insulating film 102 in Embodiment 1. The silicon oxynitride film(Si=32%, O=27%, N=24%, H=17%) is formed at 400° C. having a filmthickness of 580 nm.

An amorphous semiconductor film 103 is formed next on the baseinsulating film 102. (FIG. 4A) An amorphous semiconductor film 103 isformed out of a semiconductor film having an amorphous structure with athickness of 25 to 200 nm (preferably between 30 and 100 nm) by a knownmeans such as sputtering, LPCVD or plasma CVD. There are no limitationsplaced on the semiconductor film material, but it is preferable to formthe semiconductor film from silicon, a silicon germanium (SiGe) alloy,or the like.

Thermal crystallization using a catalyst (metal element) such as nickelis then performed, crystallizing the semiconductor film. Further, inaddition to thermal crystallization using a catalyst such as nickel, aknown crystallization process (such as laser crystallization or thermalcrystallization) may also be performed in combination. An aqueous nickelacetate solution (per weight concentration 10 ppm, volume 5 ml) isapplied to the entire surface of the film by spin coating to formcatalytic element contained layer, and the heat treatment is performedthereon for 12 hours at a temperature of 600° C. in a nitrogenatmosphere.

Further, the crystallization may be executed by performing the lasercrystallization method together with the thermal crystallization methodadding the catalytic element. If a laser crystallization method is alsoapplied, a gaseous state laser, a solid laser of a pulse oscillationlaser or a continuous oscillation can be used. Examples of gaseous statelasers are excimer lasers, Ar lasers, Kr lasers, while YAG lasers, YVO₄lasers, YLF lasers, YAlO₃ lasers, glass lasers, ruby lasers, alexandritelasers, and Ti: sapphire lasers, may be used as solid state lasers. Ifthese lasers are used, a method in which a laser beam emitted from alaser oscillator is condensed into a linear shape, rectangular shape orelliptical shape by an optical system may be used. Conditions forcrystallization may be suitably set by the operator, but the pulseoscillation frequency is set to 300 Hz and the laser energy density isset to from 100 to 800 mJ/cm² (typically between 200 and 700 mJ/cm²) ifan excimer laser is used. Further, the second harmonic is utilized if aYAG laser is used, the pulse oscillation frequency is set to form 1 to300 Hz, and the laser energy density is preferably set between 300 and1000 mJ/cm² (typically from 350 to 800 mJ/cm²). The laser beam,condensed into a linear shape with a width of 100 to 1000 μm, forexample 400 μm, may then be irradiated over the entire substratesurface. In the case that a YVO₄ laser is used, the laser light emittedfrom the continuous oscillation a YVO₄ laser of 10 W output is convertedby the non-linear optical elements, and harmonic is emitted by insertYVO₄ crystals and the non-linear optical elements in a laser oscillator.Furthermore, it is necessary for the energy density to be set to from0.01 to 100 MW/cm² (preferably from 0.1 to 10 MW/cm²) if an YVO₄ laseris used. It is then preferable to irradiate the laser light by moving astage relative to the laser beam at a speed of 0.5 to 2000 cm/s.

In the case that the catalytic element is used for the crystalline stepsof the semiconductor film, gettering is then performed in order toremove from, or reduce the concentration of, the metal element used inorder to promote crystallization in semiconductor layers that becomeactive regions. The method disclosed in Japanese Patent ApplicationLaid-open No. Hei 10-270363, and the method in which the chemical oxidefilm is formed on the crystalline semiconductor film by processing usingozone water, the gettering site containing rare gas is formed on thechemical oxide film, and the heat treatment is performed, thereby, thecatalytic element is removed to the gettering site may be applied forgettering. A silicon oxide film having a film thickness of 50 nm isformed as a mask in Embodiment 1, patterning is performed, and masks 104a to 104 c having desired shapes are obtained. A periodic table group 15element (typically phosphorous (P)) is then selectively injected intothe semiconductor film, and the impurity regions 105 a to 105 areformed. As the doping method of the impurity elements, one kind orplural kinds selected from the following method may be used; the plasmadoping method, the ion injection method, and ion shower doping method.By performing a heat treatment, the catalyst element can thus be removedfrom the semiconductor layers that becomes an active layer to theimpurity regions 105 a to 105 d, or reduced in concentration to a levelat which it does not influence the semiconductor characteristics of thesemiconductor layers. A lowered off current value, and high electricfield mobility can be obtained due to good crystallinity for TFTs havingactive regions thus manufactured. Good characteristics can thus beachieved. (FIG. 4B)

Etching of the crystalline semiconductor film is then performed to formsemiconductor layers. The insulating film is formed, and heat treatmentprocessing is performed in order to increase the crystallinity of thesemiconductor film. It is preferable to thermally oxidize an upperportion of the semiconductor film. Heat treatment is performed using anannealing furnace after forming a 20 nm thick silicon oxide film byusing an LPCVD apparatus. Upper portions of the semiconductor layers areoxidized by this process. If the silicon oxide film and the oxidizedportions of the semiconductor film layers are then etched, semiconductorlayers 106 to 108 having increased crystallinity can be obtained.

Doping of a small amount of an impurity element (boron or phosphorous)may also be performed after forming the semiconductor layers 106 to 108in order to control the TFT threshold value.

The resist masks 109 a to 109 c were formed in advance, and an impurityelement to give an n-type is selectively doped onto the semiconductorlayers by performing the second doping process. A periodic table group15 element, typically, phosphor (P) and arsenic (As) may be used as animpurity element to give the n-type. Herein, phosphor (P) is employed.Impurity elements are doped in the selected semiconductor layer becausethe masks 109 a to 109 c are formed, thereby, the high concentrationimpurity regions 110 to 112 are formed. Impurity elements imparting ann-type (hereinafter referred to as n-type impurity elements) are dopedin the high concentration impurity regions 110 to 112 at a concentrationrange from 1×10¹⁸ to 1×10²⁰/cm³. (FIG. 4C)

A first gate insulating film 113 is formed next, covering thesemiconductor layers 106 to 108. The first gate insulating film 113 isformed by an insulating film containing silicon with a thickness of 20to 150 nm using plasma CVD or sputtering. A silicon oxynitride filmhaving a film thickness of 35 nm (composition ratio: Si=32%; O=59%;N=7%; H=2%) is formed using plasma CVD in Embodiment 1. The gateinsulating film is of course not limited to a silicon oxynitride film,and other insulating films containing silicon may also be used.

Further, when using a silicon oxide film, it can be formed by plasma CVDwith a mixture of TEOS (tetraethyl orthosilicate) and O₂, at a reactionpressure of 40 Pa, with the substrate temperature set to from 300 to400° C., and by discharging at a high frequency (13.56 MHz) electricpower density of 0.5 to 0.8 W/cm². Good characteristics as a gateinsulating film can be obtained by subsequently performing thermalannealing at a temperature of 400 to 500° C. respect to the siliconoxide film that is thus manufactured.

The impurity region may be formed by doping impurity elements after thegate insulating film 113 is formed.

The conductive film having heat resistance property and having 100 to500 nm in thick is formed after that the contact hole that connects thesemiconductor layer to wirings for connecting electrically to each TFT,and the contact hole that connects gate electrode to the gate wiring 101are formed. In this embodiment, W film may be formed to have a thicknessof 400 nm by the sputtering method by using W as a target, or may beformed by the thermal CVD method by using tungsten hexafluoride (WF₆).

The conductive film is not especially limited to W, it may be formedfrom an element selected from the group consisting of Ta, W, Ti, Mo, Al,Cu, Cr, and Nd, from an alloy material having one of these elements asits main constituent, or from a chemical compound of these elements.Further, a semiconductor film, typically a crystalline silicon film intowhich an impurity element such as phosphorous is doped, may also beused, as may an AgPdCu alloy. In this embodiment, although theconductive film has a single structure, the conductive film may alsohave a laminated structure having two or more layers. In addition,triple structure in which a conductive film having low heat resistancesuch as Al is sandwiched by conductive films having high heatresistance.

The resist mask (not shown in the figures) are formed next usingphotolithography, and an etching process is performed in order to formelectrodes and wirings. An ICP (inductively coupled plasma) etchingmethod is used in Embodiment 1, and the etching conditions include: agas mixture of CF₄, Cl₂, and O₂ is used as an etching gas; the gas flowrates are set to 25:25:10 sccm, respectively; and a plasma is generatedby applying a 500 W RF electric power (13.56 MHz) to a coil shapeelectrode at 1 Pa, thereby performing etching. A 150 W RF electric power(13.56 KHz) is also applied to the substrate side (test piece stage),effectively applying a negative self-bias voltage. Thus, the gateelectrodes 114 to 116 and wirings 117 to 121 are formed. (FIG. 5A)

Next, the first insulating film 122 to cover the electrodes 114 to 116and the wirings 117 to 121 is formed. The first interlayer insulatingfilm 122 is formed out of the insulating film containing silicon to havea thickness of 100 to 200 nm by using the plasma CVD or the sputtering.In this embodiment, the oxynitride silicon film is formed to have athickness of 150 nm by plasma CVD method. Of course, the firstinterlayer insulating film 122 is not limited to the oxynitride siliconfilm, another insulating film contain other silicon in single layer orlamination layer may be used.

If necessary, the semiconductor region containing low concentrationimpurity elements in the semiconductor layer using masks may be formed.For example, the selected semiconductor layer is exposed by using resistmasks. The dosage is set from 1×10¹³ to 5×10¹⁴/cm², and doping isperformed at an acceleration voltage of 5 to 80 keV. A periodic tablegroup 15 element, typically phosphorous (P) or arsenic (As) is doped.Thus, the low concentration impurity region can be formed in theselected region of the semiconductor layer. The n-type conductivityimparting impurity element is added to the low concentration impurityregions at a concentration range of 1×10¹⁸ to 1×10²⁰ cm/³.

Heat treatment is performed next, recovering crystallinity of thesemiconductor layers, and performing activation of the impurity elementsadded to the respective semiconductor layers. Thermal annealing using anannealing furnace is performed for the heat treatment process. Thermalannealing may be performed at a temperature of 400 to 1000° C. in anitrogen atmosphere having an oxygen concentration equal to or less than1 ppm, preferably equal to or less than 0.1 ppm. Activation process isperformed by heat treatment for 30 minutes at 950° C. in Embodiment 1.Note that, in addition to thermal annealing, laser annealing using alaser such as a YAG laser, and rapid thermal annealing (RTA) can also beperformed. Further, the heat treatment process may be performed beforethat the first interlayer insulating film is formed. If the wiringmaterial is weak against heat, it is preferable to perform the heattreatment after the first interlayer insulating film is formed toprotect the wirings as Embodiment 1.

Hydrogenation processing can be performed if heat treatment is performed(at a temperature of 300 to 550° C. for 1 to 12 hours). This process isone of terminating dangling bonds in the semiconductor layers byhydrogen contained in the first interlayer insulating film 122. Thesemiconductor layers can also be hydrogenated, of course, irrespectiveof the presence of the first interlayer insulating film. As anothermeans for hydrogenation, plasma hydrogenation (using hydrogen excited bya plasma) or heat treatment for 1 to 12 hours at 300 to 450° C. withinan atmosphere containing hydrogen of 3 to 100% may also be performed.

The second interlayer insulating film 123 is formed on the firstinterlayer insulating film 122 from the inorganic insulating filmmaterials or the organic insulating materials. As the second interlayerinsulating film 123, planarizing surface film is preferably used. Aknown method to improve the planarization, for example, polishing stepsreferred to as CMP (chemical polishing) may be used. As the secondinterlayer insulating film, an acrylic resin film is formed to have athickness of 1 μm, and a portion of the first interlayer insulating filmformed on the gate electrode, the source wiring, and the drain wiring isexposed by etching. In this embodiment, although the first interlayerinsulating film and the second interlayer insulating film are formed, itcan be a single layer structure. In this case, the planarizing film ispreferably used.

In the case that the retention capacitor element is formed at theportion of drain wiring, the interlayer insulating film, and the lightshielding film that is formed later, the interval between the lightshielding film and the drain region may be reduced to make thin thethickness of the interlayer insulating film by using the CMP.

The upper portion light shielding film 124 is formed in desired shape onthe second interlayer insulating film 124 by patterning an elementselected from the group consisting of Al, Ta, W, Ti, and Cr, or an alloymaterial having one of these elements as its main constituent. The upperportion light shielding film is provided to be mesh to shield the lightexcept the opening portion. The light shielding film 125 is formed atthe driver circuit.

Subsequently, the insulating film (hereinafter referred to as thecapacitor insulating film) made from the nitride-oxide silicon or theoxynitride silicon film is formed to have a thickness of 50 to 100 nm.Since the leak current of the capacitor insulating film become large inparallel with that the dielectric constant become high if there is ahigh proportion of nitride, the content ratio is set about 1:8 to 2:1,thereby the capacitor insulating film is formed to have a thickness of50 to 100 nm.

The conductive film is formed from an element selected from the groupconsisting of Al, Ta, and W, an alloy material having one of theseelements as its main constituent or ITO. After that, etching isperformed to be a desired shape by a known method, and the upper portionlight shielding films 124, 125, the capacitor insulating film 126, 127,the conductive film 128 and 129 are formed.

Next, the film (hereinafter referred to as the planarizing film) 130 isformed so that the region where the light is permeated of the pixelelectrode is planarized by using the silicon oxide film and theinsulating film such as polyimide and acrylic. The opening portion forconnecting the pixel electrode and the conductive film is formed, and inaddition, the contact hole for connecting the pixel electrode to thedrain electrode is formed on the planarizing film 130, the interlayerinsulating film 122, and 123. The pixel electrode 131 is formed to havea thickness of 100 nm by using the transparent conductive film (ITO).Thus, the potential of the pixel electrode 131 and the conductive layer128 become the same. In the framing step of the pixel electrode, theextraction electrode 132 in the driver circuit is foamed.

As described above, the retention capacitor element can be formed thatis composed of the upper light shielding film 124, the capacitorinsulating 126, and the conductive film 128 (having the same potentialwith the pixel electrode 131). (FIG. 6)

As the present invention, forming the conductive layer 128 on thecapacitor insulating film 126 makes it possible to expansion of theregion where the storage of electric charge is possible as the retentioncapacitor element up to about two times.

Next, the conductive film 128 is etched by using the pixel electrode 131as masks to cut the sequence with the adjust pixels thereby every pixelis independent.

As mentioned above, the active matrix substrate is completed on whichthe driver circuit 204 formed out of NMOS circuit of the n-channel TFT201 and 202, and the pixel portion 205 having a pixel TFT 203 are formedon the same substrate.

At the pixel portion, the retention capacitor 206 composed of the upperlight shielding film 124, the capacitor insulating film 126, theconductive layer 128 (having the same potential with the pixel electrode131) is formed.

Since the gate electrode, source wiring, and the drain wiring are formedby the same step, the active matrix substrate formed by this means canreduce the number of steps than the conventional one. Therefore, theimprovement of yield and the reduction of costs can be realized.Further, since the physical interval between the upper light shieldingfilm and the semiconductor film is reduced, it is possible to preventthe leak current due to the light leak and the excessive diffraction.The source wiring is connected to the semiconductor film directly tominimize the number of the contact hole thereby the opening ratio can beimproved when the liquid crystal display device is manufactured.

Embodiment 2

In Embodiment 2, the manufacturing method of the semiconductor device ofdifferent structure from Embodiment 1 is described with reference toFIG. 7.

The pixel electrode 131 electrically connected with the conductive layer128 is formed on the planarizing film 130 according to Embodiment 1.Then, the large level difference formed between the adjoining pixelswhich are generated by the light shielding film 124 formed on the secondinterlayer insulating film 123, the capacitor insulating film 126, theconductive layer 128, and pixel electrode 131 is planarized with theinsulating film 401 which consists of acrylics, polyimide and the likeas shown in FIG. 7. Subsequently, although the alignment film 402 isformed, since the level difference between the adjoining pixels isburied and planarized by the insulating film 401, it is hard to produceunevenness on the alignment film 402 surface. Then, rubbing processingis performed and the substrate and opposite substrate in which TFT wasformed using sealing material (sealing agent) are stuck. And liquidcrystal is made to hold in the meantime, and an active matrix liquidcrystal display is manufactured. In addition, since this cellconstruction process uses a known method, detailed explanation isomitted.

By forming an insulating film in concave portion on a substrate asmentioned above, and the difference of the unevenness of the activematrix substrate surface formed by laminating of the various materialcan be made small. In the case of the rubbing processing performed afterforming alignment film, it is possible to minimum the rubbingirregularity, and the inferiority in alignment of liquid crystal can bemade hard to generate.

Embodiment 3

In Embodiment 3, the manufacturing method of semiconductor device ofdifferent structure from Embodiment 1 with reference to FIG. 8.

The light shielding film 301, the capacitor insulating film 302, and theconductive layer 303 according to Embodiment 1. Then, shown by the arrowof FIG. 8A, the electric conduction layer 303 is etched so that itbecomes inside a little from the light shielding film 301 and thecapacitor insulating film 302. The etching is performed by using masks,or over etching may be performed. It can prevent the generation of leakcurrent due to the conductive layer 303 being contact with the lightshielding film 301.

Furthermore, by carrying out over etching the light shielding film 311,the capacitor insulating film 312, and the conductive layer 313 in thisorder so as to be in a staircase order as shown in FIG. 8B. By carryingout etching using a mask, laminating can be made gently-sloping and thelevel difference and unevenness of pixel electrode 315 which are formedafter forming the planarized film 314 can be reduced further. Inaddition, 315 a is pixel electrode of the adjoining pixel.

As described above, the liquid crystal display device that has asufficient retention capacitor, and that can perform a good display canbe realized.

Embodiment 4

The retention capacitor element made from the conductive layer formed tohave a same potential with the light shielding film, the capacitorinsulating film, and the pixel electrode that are disclosed in thepresent invention can be formed on the light shielding film that shieldthe light except TFT as shown in Embodiment 1. In this embodiment, oneexample is described with reference to FIGS. 9 and 10.

The insulating film (not illustrated) such as the silicon oxide film,the silicon nitride film, the silicon oxynitride film are formed on thesubstrate 50, and the conductive film is formed to form the gateelectrode and patterned to obtain the gate electrodes 51 a to 51 c. Theconductive film from an element selected from the group consisting ofTa, Ti, W, Mo, Al or conductive film having one of these elements as itsmain constituent may be used. A substrate made from glass, such asbarium borosilicate glass or aluminum borosilicate glass, quartzsubstrates, single crystalline substrate, and metallic substrates andstainless steel substrates on which an insulating film is formed mayalso be used as the substrate. Further, plastic substrates having heatresistant properties capable of withstanding the processing temperaturesof Embodiment 4 may also be used.

The gate insulating films 52 a and 52 b are formed. The gate insulatingfilm may have a single structure or a lamination structure composed ofthe silicon oxide film, the silicon nitride film, the silicon oxynitridefilm.

The amorphous silicon film 53 is formed to have a thickness of 10 to 150nm by thermal CVD method, plasma CVD method, LPCVD method, evaporationmethod, or sputtering method as an amorphous semiconductor film. Sincethe gate insulating film 52 and the amorphous silicon film 53 can beformed by a same deposition method, both may be formed continuously. Thecontinuous formation does not expose to the air, so that pollution ofthe surface can be prevented and a scattering or variation in thecharacteristics or the threshold voltage of TFTs to be manufactured canbe reduced. (FIG. 9A)

Then, a catalytic element that promotes crystallization is applied tothe amorphous silicon film 53 to form a catalytic element containinglayer 54. Thereafter, heat treatment is performed to form a crystallinesilicon film. (FIG. 9B)

If a laser crystallization method is also applied, a gaseous statelaser, a solid laser of a continuous oscillation or a pulse oscillationlaser can be used. Examples of gaseous state lasers include continuousoscillation or pulse oscillation excimer lasers, Ar lasers, Kr lasers,while YAG lasers, YVO₄ lasers, YLF lasers, YAlO₃ lasers, glass lasers,ruby lasers, alexandrite lasers, and Ti: sapphire lasers, may be used assolid state lasers. In crystallizing a semiconductor film that has anamorphous structure, it is preferred to choose a continuous wavesolid-state laser and use the second harmonic to fourth hat monic of thefundamental wave in order to obtain crystals with a large grain size.Typically, the second harmonic (532 nm) or third harmonic (355 nm) of aNd:YVO₄ laser (fundamental wave: 1064 nm) is employed.

When the crystallization step is completed, the insulating film 55 toprotect the crystalline silicon film (the channel formation region) atthe later impurity doping step is formed to have a thickness of 100 to400 nm. The insulating film is formed so that the crystalline siliconfilm is not directly exposed to plasma during addition of an impurity,and so that it is possible to have delicate concentration control of theimpurity.

The highly doped n-type impurity element regions 56, 57 (source or drainregion later) where impurity elements imparting n-type is doped to thecrystalline silicon film that become an active layer of n-channel TFTlater by using a resist mask. Subsequently, the highly doped p-typeimpurity element region 58 (source or drain region later) where impurityelements imparting p-type is doped to the crystalline silicon film thatbecome an active layer of p-channel TFT later by using a resist mask. Inthe n-channel TFT and the p-channel TFT, low doped impurity elementregion (LDD region) may be formed. (FIG. 9C)

The activation process of the impurity element that is doped to thecrystalline silicon film is performed. In parallel with the activationprocess, gettering the catalyst element applied to the silicon film atthe crystalline step is performed. The heat treatment is performed atatmosphere of 5 ppm oxide concentration at a temperature of 450 to 950°C.

The insulating film on the crystalline silicon film is removed, and thecrystalline silicon film is patterned to form in a desired shape,thereby the semiconductor layers 59 to 61 is obtained. Next, theinterlayer insulating film 62 is formed. The interlayer insulating film62 is formed out of the insulating film such as the silicon oxide film,the silicon nitride film, and the silicon oxynitride film to have athickness of 500 to 1500 nm. (FIG. 9D)

The contact hole that reach the source or drain regions of each TFT isformed, and the wirings 63 to 67 are formed for connecting each TFTelectrically. And the interlayer insulating film 68 to cover the wirings63 to 67 is formed. (FIG. 10A)

The light shielding film 69 not to radiate the light to the TFT isformed. The light shielding film 69 is formed to have a thickness of 100to 200 nm by using an element selected from the group consisting of Al,Ta, W, Ti, and Cr, materials having one of these elements as its mainconstituent, or the film having high light shielding property such asblack resin and the like.

Thereafter, the capacitor insulating film 70 is formed on the lightshielding layer 69. The capacitor insulating film 70 is formed by usingeither of the silicon oxynitride film or the nitride-oxide silicon filmto have a thickness of 50 to 100 nm.

Next, the conductive film 71 is faulted on the capacitor insulating film70. The conductive layer 71 is formed by using an element selected fromthe group consisting of Al, Ta, W, Ti, and Cr, materials having one ofthese elements as its main constituent. The transparent conductive film(for example, ITO) can be used.

The planarizing film 72 is formed by using an insulating film forplanarize the region where the light of the pixel electrode istransmitted. The planarizing film 72 is performing the planarization byforming the silicon oxide film to have the thickness of 100 to 200 nm,and by using CMP method (Chemical Mechanical Polishing). After theplanarizing film 72 is formed, the contact hole to connect theconductive layer 71 and the pixel electrode is formed at the planarizingfilm 72, and the contact hole to connect the pixel electrode and thewiring 67 that become a drain electrode is formed at the planarizingfilm 72 and the interlayer insulating film 68, thereby the pixelelectrode 73 is formed. After the pixel electrode 73, the conductivelayer 71 is patterned and etched to cut the continuity to the conductivelayer 71 formed in the adjoining pixels. (FIG. 10B)

By this means, the retention capacitor element composed of the lightshielding film 69, the capacitor insulating film 70, and the conductivelayer 71 having same potential as that of the pixel electrode 73 isformed. By forming the conductive layer 71, the overlap region of thelight shielding film 69 and pixel electrode 73 can function as aretention capacitor element without futility.

Moreover, since the level difference of pixel electrode 73 is formed onthe shading film 69 by forming the planarizing film 72 as the presentinvention, the alignment disorder and the leak of light due to the leveldifference and unevenness of pixel electrode 73 can be prevented.

As mentioned above, this invention can be adopted irrespective the shapeof TFT.

Embodiment 5

In Embodiment 5, the manufacturing method of the semiconductor layerincluding the channel formation region, the source region, and the drainregion of TFT by using the semiconductor (typically silicon) film(hereinafter a high temperature polysilicon film) that is obtained byperforming heat treatment at high temperature in the semiconductor thathas TFT and a retention capacitor element shown in Embodiment 1.

The lower light shielding film and base insulating film are formed,which function also as a gate wiring according to Embodiment 1 on aquartz substrate having high heat resistant. Then, an amorphoussemiconductor film is formed on a base insulating film by a knownmethod, such as the LPCVD method, the PCVD method, or the sputteringmethod.

Subsequently, the heat treatment is performed on the amorphoussemiconductor film for 24 hours at 600° C. using a furnace to form thecrystalline semiconductor film. In addition, although an oxide siliconefilm is formed on the semiconductor film surface in this crystallizationprocessing, there is no problems because it is a very thin filmremovable by etching and the like.

The heat treatment is performed for forming a gate insulating film afterremoving the oxide film formed on the surface of the crystallinesemiconductor film. The crystalline semiconductor film is heat treatedat 900 to 1050° C., and an oxide film is formed on the surface of thecrystalline semiconductor film. This oxide silicone film is used for agate insulating film. The oxide silicone film is finally formed on thesurface of crystalline semiconductor film by performing heat treatmenton the crystalline semiconductor film to have thickness of 30 to 50 nm.

The crystal semiconductor film obtained by high temperature heattreatment has high crystallinity. By using the semiconductor film havinghigher degree of the electrical field effect movement with thesemiconductor layer including the channel formation region, the sourceregion, and the drain region is obtained, TFT with the outstandingcharacteristic can be realized. Moreover, the semiconductor devicehaving high reliability can be realized by using this TFT for a circuit.This embodiment can be used by combining with Embodiments 1 to 4.

Embodiment 6

In this embodiment, a description will be given of an example in which,in a semiconductor device having the structure shown in Embodiment 1which includes a thin film transistor and a storage capacitor element, asemiconductor layer including a channel formation region, a sourceregion, and drain region of the thin film transistor is manufactured byusing a crystalline semiconductor film obtained through laser lightapplication.

According to the manner of Embodiment 1, a lower light-shielding filmalso serving as a gate line and a base insulating film are formed on asubstrate. Subsequently, an amorphous semiconductor film is formed onthe base insulating film by a well-known method such as an LPCVD method,a PCVD method, or a sputtering method. Here, employed as the substrateis a substrate made of glass such as barium borosilicate glass andaluminoborosilicate glass which are represented by Corning #7059 glassand #1737 glass manufactured by Corning Incorporated. Also, a quartzsubstrate, a single crystal silicon substrate, or a metal substrate or astainless steel substrate with the insulating film formed on the surfacethereof can be adopted. Further, a plastic substrate having a high heatresistance can be adopted.

Following this, the amorphous semiconductor film is irradiated with alaser light. As the laser to be used, a gas laser or a solid laser ofcontinuous oscillation or pulse oscillation is used. As the gas laser,there is used an excimer laser, an Ar laser, a Kr laser, or the like. Asthe solid laser, there is used a YAG laser, a YVO₄ laser, a YLF laser, aYAlO₃ laser, a glass laser, a ruby laser, an alexandrite laser, a Ti:sapphire laser, or the like.

Note that, as the solid laser, there is applied a laser using crystalsuch as YAG, YVO₄, YLF, or YAlO₃ doped with Cr, Nd, Er, Ho, Ce, Co, Ti,or Tm. A fundamental wave of the laser concerned varies depending on adoped material and a laser light having the fundamental wave of around 1μm is obtained. A harmonic with respect to the fundamental wave can beobtained by using a nonlinear optical element.

Upon crystallization of the amorphous semiconductor film, in order toobtain crystal with a large grain size, it is preferable that the solidlaser capable of continuous oscillation is used and a second harmonic toa fourth harmonic with respect to the fundamental wave are applied. As atypical example thereof, the second harmonic (532 nm) or the thirdharmonic (355 nm) of an Nd:YVO₄ laser (fundamental wave: 1064 nm) isapplied.

Here, as an example, a method of performing the crystallization usingthe YVO₄ laser will be described. The laser light emitted from the YVO₄laser of continuous oscillation with an output of 10 W is converted intothe harmonic by the nonlinear optical element. Further, it is alsopossible that the YVO₄ crystal and the nonlinear optical element are putinto a resonator to generate the harmonic. Then, after being shaped intoa laser light preferably in the form of rectangle or ellipse on theirradiation surface through an optical system, the laser light isapplied to the target body for processing. At this time, an energydensity of about 0.01 to 100 MW/cm² (preferably, 0.1 to 10 MW/cm²) isrequired. Then, a laser light is applied in such a manner that thesemiconductor film is moved relative to the light at a speed of about0.5 to 2000 cm/s.

The crystalline semiconductor film thus obtained through a laser lightirradiation is high in crystallinity and a semiconductor film in whichhigher field effect mobility can be obtained is used for thesemiconductor layer including the channel formation region, the sourceregion, and the drain region. Thus, the TFT having superiorcharacteristics can be attained, and further, by applying the TFT to thecircuit, a semiconductor device with a high reliability can be realized.This embodiment can be implemented in combination with Embodiments 1 to4.

Embodiment 7

Through the application of the present invention, various electricappliances can be completed in which an active matrix liquid crystaldisplay device (liquid crystal display) is incorporated into a displayportion.

As an example of the above-mentioned electric appliances, there can begiven a projector (rear type or front type), a video camera, a digitalcamera, a head mounted display (goggle type display), a personalcomputer, a personal digital assistant (mobile computer, cellular phone,electronic book, etc.), or the like. An example thereof is shown inFIGS. 11A to 13C.

FIG. 11A shows a front type projector that includes a projection device2601, a screen 2602, etc.

FIG. 11B shows a rear type projector that includes a main body 2701, aprojection device 2702, a mirror 2703, a screen 2704, etc.

Note that, FIG. 11C is a view showing an example of structures of theprojection devices 2601 and 2702 in FIGS. 11A and 11B. The projectiondevices 2601 and 2702 are composed of a light source optical system2801, mirrors 2802 and 2804 to 2806, dichroic mirrors 2803, a prism2807, a liquid crystal display device 2803, a phase difference plate2809, and a projection optical system 2810. The projection opticalsystem 2810 is constituted of an optical system including a projectionlens. In this embodiment, a three-CCD type is shown by way of example,but there is put no particular limitation thereon. For example, asingle-CCD type may be employed. Also, the performer may appropriatelyprovide, in some midpoint of an optical path indicated by the arrow ofFIG. 11C, an optical system such as an optical lens, a film having apolarization function, a film for adjusting a phase difference, or an IRfilm.

Also, FIG. 11D is a view showing an example of a structure of the lightsource optical system 2801 shown in FIG. 11C. In this embodiment, thelight source optical system 2801 is constituted of a reflector 2811, alight source 2812, lens arrays 2813, 2814, a polarization conversionelement 2815, and a condensing lens 2816. Note that, the light sourceoptical system shown in FIG. 11D is only employed as an example, andthere is put no particular limitation thereon. For example, theperformer may appropriately provide in the light source optical systemthe optical system such as the optical lens, the film having apolarization function, the film for adjusting a phase difference, or theIR film.

By using the present invention, the light applied to the thin filmtransistor can be shielded by the light-shielding film, so that anoptical leak current can be suppressed even if a strong light adopted inthe projector is irradiated. In addition, the capacitor element having asufficient storage capacitor is formed, which makes it possible to holda signal and to prevent an uneven display. As a result, a definitedisplay with a high quality can be achieved. Moreover, a sufficientcapacitor element can be formed without reducing an opening ratio, sothat low power consumption can be realized in the light source whilemaintaining sufficient luminance.

FIG. 12A shows a personal computer that includes a main body 2001, animage input portion 2002, a display portion 2003, a key board 2004, etc.It is possible that the liquid crystal display device of the presentinvention is adapted to the display portion 2003 to thereby complete thepersonal computer. FIG. 12B shows a mobile computer that includes themain body 2001, a camera portion 2102, an image receiving portion 2103,an operation switch 2104, a display portion 2105, etc. It is possiblethat the liquid crystal display device of the present invention isadapted to the display portion 2105 to thereby complete the mobilecomputer. FIG. 12C shows a player using a recording medium in which aprogram is recorded (hereinafter referred to as recording medium), whichincludes a main body 2201, a display portion 2202, a speaker portion2203, a recording medium 2204, an operation switch 2205, etc. Here, inthis player, employed as the recording medium is a DVD (digitalversatile disc), a CD, or the like. Through this, appreciation of musicor movie, a game, or an Internet can be attained. It is possible thatthe liquid crystal display device of the present invention is adapted tothe display portion 2202 to thereby complete the player using therecording medium. In these electric appliances, through the applicationof the present invention, the defect in orientation of the liquidcrystal due to the steps or unevennesses in the region through which alight passes in the pixel electrode can be eliminated. In addition, thecapacitor element capable of obtaining a sufficient storage capacitorcan be formed and thus, even if the leak current is generated, thedisplay signal can be hold, thereby attaining a definite display withoutcausing uneven display. Also, even if the capacitor element is fanned,the opening ratio can be maintained high, so that high luminance can beobtained and the power consumption of the light source used for thedisplay can be reduced. This contributes to the low power consumption inthe whole electric appliance.

FIG. 12D shows a video camera that includes a main body 2301, a displayportion 2302, a voice input portion 2303, operation switches 2304, abattery 2305, an image receiving portion 2306, etc. It is possible thatthe liquid crystal display device of the present invention is adapted tothe display portion 2302 to thereby complete the video camera. FIG. 12Eshows a digital camera, which includes a main body 2401, a displayportion 2402, an eyepiece portion 2403, operation switches 2404, animage receiving portion (not shown), etc. It is possible that the liquidcrystal display device of the present invention is adapted to thedisplay portion 2402. FIG. 12F shows a goggle type display, whichincludes a main body 2501, display portions 2502, an arm portion 2503,etc. It is possible that the liquid crystal display device of thepresent invention is adapted to the display portion 2502. FIG. 13A showsa cellular phone, which includes a display panel 3001 and an operationpanel 3002. The display panel 3001 and the operation panel 3002 areconnected through a connection portion 3003, in which angle θ between aplane in which a display portion 3004 of the display panel 3001 isformed and a plane in which operation keys 3006 of the operation panel3002 are formed can be arbitrarily changed. Further, the cellular phoneincludes a voice output portion 3005, the operation keys 3006, a powersupply switch 3007, and a voice input portion 3008. It is possible thatthe liquid crystal display device of the present invention is adapted tothe display portion 3004 to thereby complete the cellular phone. FIG.13B shows a portable book (electronic book), which includes a main body3101, display portions 3102, 3103, a recording medium 3104, an operationswitch 3105, an antenna 3106, etc. It is possible that the liquidcrystal display device of the present invention is adapted to thedisplay portions 3102, 3103, to thereby complete the portable book.Thus, according to the present invention, the defect in orientation ofthe liquid crystal can be decreased, so that a definite display can berealized without causing uneven display. Further, the capacitor elementcan be formed while maintaining the opening ratio high, and thus highluminance can be obtained and the power consumption of the light sourceused for the display can be reduced. This makes it possible to realizelow power consumption in the whole electric appliance. Therefore, acompact battery with a reduced weight suffices therefor, which makes itpossible to reduce the whole electric appliance in weight.

FIG. 13C show a display, which includes a main body 3201, a support3202, a display portion 3203, etc. It is possible that the liquidcrystal display device of the present invention is adapted to thedisplay portion 3203 to thereby complete the display. According to thepresent invention, it is possible that the region through which a lightpasses (region contributing to the display) of the pixel electrode isflattened to make the step formed on the light-shielding film, so thatthe defect in orientation of the liquid crystal and the uneven displaycan be eliminated. Further, since the storage capacitor element can beformed without reducing the opening ratio, a display can be obtainedwith high luminance and definition.

As described above, an application range of the present invention isextremely wide and the present invention can be adapted in order tocomplete the electric appliances in various fields. Also, the electricappliances of this embodiment can be attained by using any liquidcrystal display device manufactured according to Embodiments 1 to 6 incombination.

As disclosed in the present invention, the capacitor insulating film isformed on the light-shielding film, the conductive layer is formed onthe capacitor insulating film, and the conductive layer and the pixelelectrode are electrically connected so as to have the same potential,whereby all the region in which the light-shielding film and the pixelelectrode are overlapped can be used as the storage capacitor elementeffectively. Also, through the application of the present invention, thestorage capacitor element having a sufficient capacitance can be formedwithout reducing the opening ratio of the pixel.

Note that, the present invention is effective since, irrespective of theshape of the TFT, a capacitor wiring is formed on the light-shieldingfilm for shielding the TFT from the light which is made of theconductive material, the conductive layer is formed on the capacitorwiring, and the potential is applied from the pixel electrode to theconductive layer to thereby attain function of the storage capacitorelement.

1-35. (canceled)
 36. A semiconductor device comprising: a substratehaving a pixel portion and a driver circuit portion; a first conductivefilm over the substrate; a first insulating film over the firstconductive film; a thin film transistor over the first insulating film;a second insulating film over the thin film transistor; a capacitor overthe second insulating film; a third insulating film over the capacitor,the third insulating film having a planarized surface; a pixel electrodeon the third insulating film, the pixel electrode electrically connectedto the thin film transistor; and an electrode in the driver circuitportion, the electrode comprising a same material of the pixelelectrode, wherein the first conductive film is electrically connectedwith the thin film transistor.
 37. A semiconductor device according toclaim 36, wherein the substrate comprises a material selected from thegroup consisting of glass, quartz, silicon, metal and plastic.
 38. Asemiconductor device according to claim 36, wherein the first conductivefilm comprises a material selected from the group consisting of Ta, W,Ti, Mo, Al, Cu, Cr, and Nd.
 39. A semiconductor device according toclaim 36, wherein the first conductive film is electrically connected toa gate electrode of the thin film transistor.
 40. A semiconductor deviceaccording to claim 36, wherein at least one part of the thin filmtransistor is overlapped with a part of the capacitor.
 41. Asemiconductor device according to claim 36, wherein at least a channelregion of the thin film transistor is overlapped with a part of thecapacitor.
 42. A semiconductor device according to claim 36, wherein thethird insulating film comprises at least one of an inorganic insulatingfilm and an organic insulating film.
 43. A semiconductor deviceaccording to claim 36, wherein the pixel electrode is electricallyconnected to the capacitor.
 44. A semiconductor device according toclaim 36, wherein the pixel electrode comprises a transparent conductivefilm.
 45. A semiconductor device according to claim 36, wherein thesemiconductor device is applied to an electric appliance selected fromthe group consisting of a projector, a personal computer, a videocamera, a goggle type display and a display.
 46. A semiconductor devicecomprising: a substrate having a pixel portion and a driver circuitportion; a first conductive film over the substrate; a first insulatingfilm over the first conductive film; a thin film transistor over thefirst insulating film; a second insulating film over the thin filmtransistor; a capacitor over the second insulating film, the capacitorcomprising a lower conductive layer, a capacitor insulating film, and anupper conductive layer; a third insulating film over the capacitor, thethird insulating film having a planarized surface; a pixel electrode onthe third insulating film, the pixel electrode electrically connected tothe thin film transistor; and an electrode in the driver circuitportion, the electrode comprising a same material of the pixelelectrode, wherein at least one part of the thin film transistor isoverlapped with a part of the capacitor.
 47. A semiconductor deviceaccording to claim 46, wherein the substrate comprises a materialselected from the group consisting of glass, quartz, silicon, metal andplastic.
 48. A semiconductor device according to claim 46, wherein thefirst conductive film comprises a material selected from the groupconsisting of Ta, W, Ti, Mo, Al, Cu, Cr, and Nd.
 49. A semiconductordevice according to claim 46, wherein the first conductive film iselectrically connected to a gate electrode of the thin film transistor.50. A semiconductor device according to claim 46, wherein at least achannel region of the thin film transistor is overlapped with the partof the capacitor.
 51. A semiconductor device according to claim 46,wherein the lower conductive layer comprises a light-shielding film. 52.A semiconductor device according to claim 46, wherein the thirdinsulating film comprises at least one of an inorganic insulating filmand an organic insulating film.
 53. A semiconductor device according toclaim 46, wherein the pixel electrode is electrically connected to thecapacitor.
 54. A semiconductor device according to claim 46, wherein thepixel electrode comprises a transparent conductive film.
 55. Asemiconductor device according to claim 46, wherein the semiconductordevice is applied to an electric appliance selected from the groupconsisting of a projector, a personal computer, a video camera, a goggletype display and a display.
 56. A semiconductor device comprising: asubstrate having a pixel portion and a driver circuit portion; a firstconductive film over the substrate; a first insulating film over thefirst conductive film; a first thin film transistor and a second thinfilm transistor over the first insulating film, the first thin filmtransistor and the second thin film transistor located in the pixelportion and the driver circuit portion, respectively; a secondinsulating film over the first thin film transistor and the second thinfilm transistor; a capacitor over the second insulating film; a thirdinsulating film over the second insulating film and the capacitor, thethird insulating film having a planarized surface; a pixel electrodeover the third insulating film; and an electrode electrically connectedto the second thin film transistor in the driver circuit portion, theelectrode comprising a same material of the pixel electrode.
 57. Asemiconductor device according to claim 56, wherein the first conductivefilm is electrically connected to at least one of the first thin filmtransistor and the second thin film transistor.
 58. A semiconductordevice according to claim 56, wherein at least one part of the firstthin film transistor is overlapped with a part of the capacitor.
 59. Asemiconductor device according to claim 56, wherein at least a channelregion of the first thin film transistor is overlapped with a part ofthe capacitor.
 60. A semiconductor device according to claim 56, whereinthe pixel electrode is electrically connected to the capacitor.
 61. Asemiconductor device according to claim 56, wherein the first conductivefilm comprises a material selected from the group consisting of Ta, W,Ti, Mo, Al, Cu, Cr, and Nd.
 62. A semiconductor device according toclaim 56, wherein the third insulating film comprises at least one of aninorganic insulating film and an organic insulating film.
 63. Asemiconductor device according to claim 56, wherein the pixel electrodecomprises a transparent conductive film.
 64. A semiconductor deviceaccording to claim 56, wherein the substrate comprises a materialselected from the group consisting of glass, quartz, silicon, metal andplastic.
 65. A semiconductor device according to claim 56, wherein thesemiconductor device is applied to an electric appliance selected fromthe group consisting of a projector, a personal computer, a videocamera, a goggle type display and a display.
 66. A semiconductor devicecomprising: a substrate having a pixel portion and a driver circuitportion; a first conductive film over the substrate; a first insulatingfilm over the first conductive film; a first thin film transistor and asecond thin film transistor over the first insulating film, the firstthin film transistor and the second thin film transistor located in thepixel portion and the driver circuit portion, respectively; a secondinsulating film over the first thin film transistor and the second thinfilm transistor; a capacitor over the second insulating film, thecapacitor comprising a lower conductive layer, a capacitor insulatingfilm, and an upper conductive layer; a third insulating film over thesecond insulating film and the capacitor, the third insulating filmhaving a planarized surface; a pixel electrode over the third insulatingfilm; and an electrode electrically connected to the second thin filmtransistor in the driver circuit portion, the electrode comprising asame material of the pixel electrode.
 67. A semiconductor deviceaccording to claim 66, wherein the substrate comprises a materialselected from the group consisting of glass, quartz, silicon, metal andplastic.
 68. A semiconductor device according to claim 66, wherein thefirst conductive film comprises a material selected from the groupconsisting of Ta, W, Ti, Mo, Al, Cu, Cr, and Nd.
 69. A semiconductordevice according to claim 66, wherein the first conductive film iselectrically connected to at least one of the first thin film transistorand the second thin film transistor.
 70. A semiconductor deviceaccording to claim 66, wherein at least a channel region of the firstthin film transistor is overlapped with a part of the capacitor.
 71. Asemiconductor device according to claim 66, wherein the lower conductivelayer comprises a light-shielding film.
 72. A semiconductor deviceaccording to claim 66, wherein the third insulating film comprises atleast one of an inorganic insulating film and an organic insulatingfilm.
 73. A semiconductor device according to claim 66, wherein thepixel electrode is electrically connected to the capacitor.
 74. Asemiconductor device according to claim 66, wherein the pixel electrodecomprises a transparent conductive film.
 75. A semiconductor deviceaccording to claim 66, wherein the semiconductor device is applied to anelectric appliance selected from the group consisting of a projector, apersonal computer, a video camera, a goggle type display and a display.